(1) Field of the Invention
The present invention relates to decontaminating coatings, and more particularly to decontaminating coatings in which the decontaminating effect is triggered by the application of a signal to the coating.
(2) Description of the Related Art
The need to protect or cleanse surfaces of contaminants is important in many different contexts. It is well known that equipment, floors, walls, counters, and the like, in hospitals and health care facilities must be sanitized regularly. Food service equipment and facilities must be cleaned and sanitized. Certain processing equipment in some manufacturing and/or diagnostic facilities demands a high level of cleanliness and freedom from contaminants.
In a different context, it is important to be able to decontaminate or neutralize chemical and biological warfare agents in order to reduce or avoid grave injury or death of human beings. In this context, the purposeful deployment of extremely aggressive and harmful chemical or biological agents is meant to cause massive contamination of exposed surfaces, which can remain dangerous to living subjects for as long as the harmful agent retains its potency and remains on the surface. Not only are organizations such as the armed forces interested in dealing with such harmful agents, but organizations such as post offices, package delivery services, and the like, are also involved.
Many sanitization and cleaning methods and compounds are well known in the art that meet the needs of common cleaning and sanitizing requirements. More recently, greater attention has been placed on improved and different techniques and compounds that can be used for the decontamination of surfaces and articles contaminated with chemical and biological warfare agents.
In U.S. Pat. No. 6,316,015, Rondelez et al., describe hyperbactericidal surfaces that are formed by binding antibiotic, bactericidal, viricidal or fungicidal molecules to the surface via a linker or spacer molecule.
In U.S. Pat. No. 6,343,425, Sias et al. describe the application of hydrogen peroxide that is activated by an electronic plasma containing 2H+ and 2e− for the cleaning and sterilization of articles having particulates adhered thereto. Further information about this method was found under the title “A2C2” at www.a2c2.com/articles/lifejan02 (Jun. 16, 2005).
Hoffman et al., in U.S. Pat. No. 6,455,751, describe oxidizer gels for detoxification of chemical and biological agents. The gels contain oxidizing agents and thickening or gelling agents and are applied directly to a contaminated area. The high viscosity of the gel allows it to remain on tilted or contoured surfaces without flowing off. After decontamination, the residue can be washed away.
In U.S. Pat. No. 6,525,237, Purdon et al. describe a broad spectrum decontamination formulation that contains an active decontamination agent, a co-solvent, a buffer system, and a surfactant. The formulation can be dispensed as a foam onto contaminated surfaces.
Formulations for neutralization of chemical and biological toxants are also described by Tadros et al. in U.S. Pat. No. 6,566,574. The formulations can be applied as foams to contaminated surfaces and contain at least two solubilizing compounds and at least one reactive compound, which neutralize the toxant.
In U.S. Pat. No. 6,692,694, Curry et al. describe a process that involves spraying a contaminated surface with a formulation that includes an aerosol photosensitizer and then illuminating the surface, preferably with UV light, to cause the photodecomposition of chemical or biological contaminants.
Examples of more recent work include methods that involve spraying contaminated areas with a cloud of a material containing a photocatalytic oxidizing substance and then shining a high intensity beam of light of a certain wavelength that triggers a catalyzed activation that releases free radicals of the oxidizing substance (U.S. Patent Application Publ. 20040120844 A1). U.S. Patent Application Publ. 20040076543 A1 discusses a decontamination system in which a high electrical field applied across the electrodes of reactor cores causes the decomposition of contaminants that are passed through the gap region between the electrodes. Biological active coatings are discussed in U.S. Patent Application Publ. 20040109853, wherein the coatings comprise a biomolecule composition that includes a phosphoric triester hydrolase, which breaks down organophosphorous compounds of the type used in chemical warfare agents. Self-cleaning, self-decontaminating coatings are also discussed in U.S. Patent Application Publ. 2004/0224145 AI. In this coating, a transition metal oxide, such as the anatase form of TiO2, is used to photochemically catalyze the formation of hydroxyl radicals by activation with UV radiation. The hydroxyl radicals cleanse the surface and degrade contaminants on the surface of the coating.
Recent work by Collins and others has been reported in which the activation of hydrogen peroxide yields an activated hydrogen peroxide species that is capable of the total destruction of certain harmful chlorophenols. See, e.g., Gupta, S. S. et al., Science, 296:326-328 (2002), and supplementary material for that article found at www.sciencemag.org, and Ghosh A. et al., Pure Appl. Chem., 73(1):113-118 (2001). In the system described by these workers, certain homogenous amide-containing macrocyclic compounds, such as tetraamidomacrocyclic ligand (TAML®) iron catalysts, are contacted with hydrogen peroxide at ambient conditions of temperature and pressure to form activated hydrogen peroxide species that destroy contaminants such as pentachlorophenol and 2,4,6-trichlorophenol in minutes. The TAML® catalysts are described as being stable to exposure to hydrogen peroxide and as functioning in ppm (parts per million) concentrations in water to activate hydrogen peroxide to perform a broad array of oxidation reactions and some hydrolysis and/or perhydrolysis reactions. Further information on the synthesis and structures of such TAML® catalysts is found in U.S. Pat. Nos. 5,847,120 and 6,054,580. TAML® is a registered trademark of Carnegie Mellon University, Pittsburgh Pa.
This group has also reported the application of this same system for the oxidative destruction of alkyl sulfides and disulfides (Collins, T. J. et al., Abstr. of Papers, 228th ACS National Mtg., Philadelphia, Pa. USA, Aug. 22-26, 2004, American Chemical Society, Washington, D.C. (2004)), for the degradation of organophosphorous compounds (Collins, T. J. et al., Abstr. of Papers, 226th ACS National Mtg., New York, N.Y., USA, Sep. 7-11, 2003, American Chemical Society, Washington, D.C. (2003)), for the deactivation of bacterial spores as surrogates for biological warfare agents (Banerjee, D. et al., Abstr. 35th Central Regional Mtg. of the Am. Chem. Soc., Pittsburgh, Pa., USA, Oct. 19-22, 2003, American Chemical Society, Washington, D.C. (2003)), and for the bleaching of azo dyes (Gupta, S. S. et al., Book of Abstracts, 217th ACS National Meeting, Anaheim, Calif., Mar. 21-25, 1999, Am. Chem. Soc., Washington D.C. (1999).
Despite the significant advances that have been made in surface decontamination technology in recent years, there remain a number of limitations in the application of available methods. For example, many of the present systems require application after a contaminating event. If the event is a significant chemical or biological warfare event, persons applying the decontamination remedy are themselves put at risk. It would be useful, therefore, to provide a decontamination system that could be put in place before a contaminating event occurs. It would be even more useful if such a system could be activated either in anticipation of an imminent contaminating event, or at any time after such an event had occurred. Moreover, it would be useful if such a system did not itself present a danger to humans or animals, such as a cloud of corrosive or toxic material, or a liquid or gel that made coated surfaces harmful to touch. It would also be useful if such a method could be activated when desired and, after the contamination danger had passed, could be deactivated and would return to a state that was harmless to humans and animals. It would be even more useful if a system that facilitated such a method could easily be returned to a state of readiness for use after an initial use. Furthermore, it would be useful if the method and the system was durable, in other words, would persist and not be leached out or washed off of protected surfaces by rain, fog, snow, or other normal environmental events. It would also be useful it such a method or system could be applied to almost any type of surface, for example to flexible materials, such as fabrics as well as to hard surfaces, such as vehicles, counter tops, walls, floors, and the like.